Partial Function Application -- Advantages over normal function?

Terry Reedy tjreedy at udel.edu
Mon Jul 18 22:17:28 CEST 2011


On 7/18/2011 3:23 PM, woooee wrote:
> Partial can be used in a GUI program, like Tkinter, to send arguments
> to functions.  There are other ways to do that as well as using
> partial.  The following program uses partial to send the color to the
> change_buttons function.
> from Tkinter import *
> from functools import partial
>
> class App:
>     def __init__(self, parent):
>      self.my_parent = parent
>      self.my_parent.geometry("200x100+10+10")
>
>      self.R = list()
>      for ctr, color in enumerate(("Red", "Blue", "Green")):
>          btn = Radiobutton(self.my_parent, text=color, value=ctr+1,
>                            command=partial(self.change_buttons, color))
>          btn.grid(row = 2, column = ctr+1)

This is a nice illustration. For future reference: enumerate now takes a 
start value as second parameter. Given as 1, you do not need to remember 
to add 1 for each usage.

     for ctr, color in enumerate(("Red", "Blue", "Green"),1):
         btn = Radiobutton(self.my_parent, text=color, value=ctr,
                           command=partial(self.change_buttons, color))
         btn.grid(row = 2, column = ctr)

>          btn.deselect()
>          self.R.append(btn)
>      self.R[0].select()
>      self.change_buttons("Red")
>
>     def change_buttons(self, color):
>         self.my_parent.configure(bg=color)
>         for btn in self.R:
>              btn.configure(bg=color)
>
> if __name__ == "__main__":
>      root = Tk()
>      root.title ("Color Option")
>      app = App(root)
>      root.mainloop()


-- 
Terry Jan Reedy




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